244 



VERTEBRATE ANIMALS OF THE UNITED STATES 



is a constant and very important character, and is given in this book 

 in the following manner, the figures referring to the number of incisor, 

 canine, premolar and molar teeth on each side of the jaws: ''dentition 

 2,/2„ i/i, 4/4, 2/3," the meaning of which is that on each side of the 

 mouth there are 3 upper and 3 lower incisors, i upper and i lower 

 canine, 4 upper and 4 lower premolars and 2 upper and 3 lower molars. 



L < 



Fig. 139. — Skull of dog, showing dentition, the formula of which is 3/3, i/i, 4/4, 2/3: A 

 side view; B, upper jaw; c, canines; i, incisors; m, molars; pm, premolars. 



This is the dentition of the dog (Fig. 139), which has thus 10 teeth in 

 the upper jaw on each side and 1 1 teeth in the lower jaw on each side 

 or 20 teeth in the upper jaw on both sides and 22 teeth in the lower jaw 

 on both sides, and 42 teeth altogether. The dentition of the pocket 

 gopher is i/i, 0/0, i/i, 3/3, the meaning of which is that this animal has 

 I upper and i lower incisor on each side or 2 upper and 2 lower incisors 



